Complex systems such as an electronically controlled diesel engine typically utilize diagnostic trouble codes (DTCs), failure mode indicators (FMIs), suspect parameter numbers (SPNs), and/or other notifications to assist a service technician in diagnosing a problem with the system. DTCs will be used generally to encompass these various notifications, including for example failure, fault and/or error codes. One failure mode will often result in multiple DTCs. For example, a problem with a regulated sensor voltage supply shared by several sensors may result in a voltage out of range DTC for each sensor as well as a DTC indicating a problem with the regulated voltage supply. The sensor voltage out of range DTCs are symptoms of the root cause which is a problem with the regulated voltage supply. The service technician makes the decision on which DTC to diagnose first when there are multiple DTCs present. If the technician begins diagnosing the system by troubleshooting one of the symptom DTCs instead of the root cause DTC, the time and effort, and possibly cost, required to diagnose the system will be increased.
In another example, modeled or virtual sensors typically use information from physical or real sensors to calculate virtual sensor data. A problem with a physical sensor which is used in the calculation of a virtual sensor can result in a DTC for the virtual sensor along with a DTC for the physical sensor. Without engineering-level information, the interaction between physical sensors and virtual sensors would likely not be evident to a service technician. Therefore, the technician may start diagnosing the DTC for the virtual sensor before diagnosing the root cause which is the DTC for the physical sensor.
In addition to electrical issues, mechanical problems can result in multiple DTCs. For example, diesel engine fuel system pressure sensors are typically located in the low-pressure fuel supply system and the high-pressure (i.e. common rail) system. A restricted fuel filter can cause DTCs for both the low-pressure and high-pressure fuel systems. A DTC for the low-pressure fuel system could become active indicating a problem has been detected, and then at a later time the DTC for the high-pressure fuel system could become active. However, both DTCs for the low-pressure and high-pressure fuel systems could be active when the technician begins diagnosing the problems. An inexperienced technician may begin the diagnosis by troubleshooting the active high-pressure fuel system DTC and ignore the previously active low-pressure fuel system DTC, leading to needless replacement of expensive components.
Some system manuals provide service diagnostic procedures with troubleshooting sequence lists for each DTC diagnostic procedure. This static list requires a technician to compare the list of DTCs to be diagnosed first with the current list of active or previously active DTCs on the machine. There is no recommendation in the service information providing the technician information on where to start when there are several DTCs present on the same machine.
Some manufacturers have on-line tools that provide a technician with a recommendation for a multiple DTC diagnostic sequence. However, these tools require the technician to manually enter each DTC present on the machine into the on-line tool and do not appear to be application specific. Other systems provide a process of generating test sequences to diagnose a problem, but not a means of prioritizing which DTC to diagnose first.
It would be desirable to have a system that processes multiple DTCs for an application and provides a prioritized and targeted list for a technician regarding which DTC is likely indicating the root cause problem for the application, thus reducing diagnostic time and cost.